1. Field of the Invention
The present invention relates to the art of controlling the feeding of substrates with respect to a plurality of processing chambers of a substrate processing apparatus such as a semiconductor fabrication apparatus for forming films on semiconductor substrates or an LCD (liquid crystal display) fabrication apparatus for forming films on glass substrates for LCD.
2. Description of the Related Art
One known substrate processing apparatus for successively processing substrates in a plurality of processing chambers finds its use as an LCD fabrication apparatus of the single-substrate in-line processing type which processes a substrate or a small number of substrates successively as shown in FIG. 17 of the accompanying drawings.
The LCD fabrication apparatus shown in FIG. 17 has an atmospheric substrate feeder T1 coupled to a loading cassette stand S1, an auxiliary substrate loading chamber L1 coupled to the atmospheric substrate feeder T1 by a gate valve LV1, a vacuum substrate feeder T2 coupled to the auxiliary substrate loading chamber L1 by a gate valve LV2, and an auxiliary substrate heating chamber H coupled to the vacuum substrate feeder T2.
A vacuum substrate feeder T3 is coupled to the auxiliary substrate heating chamber H by a gate valve LV3. First, second, and third film growing chambers R1, R2, R3 are coupled to the vacuum substrate feeder T3 by respective gate valves LV4, LV5, LV6.
A vacuum substrate feeder T4 is coupled to the third film growing chamber R3 by a gate valve LV7. Fourth and fifth film growing chambers R4, R5 are coupled to the vacuum substrate feeder T4 by respective gate valves LV8, LV9. A buffer chamber B1 is coupled to the vacuum substrate feeder T4. A vacuum substrate feeder T5 is coupled to the buffer chamber B1. Sixth, seventh, and eighth film growing chambers R6, R7, R8 are coupled to the vacuum substrate feeder T5 by respective gate valves LV10, LV11, LV12. A vacuum substrate chamber T6 is coupled to the eighth film growing chamber R8 by a gate valve LV13.
An auxiliary substrate unloading chamber L2 is coupled to the vacuum substrate chamber T6 by a gate valve LV14. An atmospheric substrate feeder T7 is coupled to the auxiliary substrate unloading chamber L2 by a gate valve LV15. An unloading cassette stand S2 is coupled to the atmospheric substrate feeder T7.
The vacuum substrate feeders are housed in feed chambers. The film growing chambers serve as processing chambers for growing films on substrates therein. The heating chamber serves as a chamber for heating a substrate therein. Therefore, the chambers of the LCD fabrication apparatus serve as processing chambers for processing substrates in predetermined fashions.
A substrate loaded into the LCD fabrication apparatus is processed in the processing chambers as it is fed successively therethrough by the feeders. After desired films have been formed on the substrate, the substrate is unloaded from the LCD fabrication apparatus.
The feeding of substrates successively through the processing chambers and the processing of those substrates in the processing chambers are controlled by a controller (not shown).
Efforts have been made to increase the throughput of the LCD fabrication apparatus. For example, identical films are formed on substrates in the first and second film growing chambers R1, R2. Since the same films are formed on the substrates in the two film growing chambers, the throughput can be increased when successive substrates are introduced into the LCD fabrication apparatus.
For such simultaneous processing, the substrates need to be fed into the first and second film growing chambers R1, R2 by the vacuum substrate feeder T3. Consequently, the vacuum substrate feeder T3 is subject to an conflict between feed job requirements for feeding substrates into the two film growing chambers simultaneously.
The LCD fabrication apparatus of the single-substrate in-line processing type takes up a relatively large installation space and is relatively expensive because it has many substrate feeders (seven feeders in FIG. 17). To eliminate these drawbacks, there have been employed substrate processing apparatus of the single-substrate cluster type in recent years.
The substrate processing apparatus of the single-substrate cluster type comprises a plurality of processing chambers coupled to a main frame which houses substrate feeders. Some of the processing chambers serve as film growing chambers for processing substrates identically, and substrates are fed into these film growing chambers by one substrate feeder.
Inasmuch as such one substrate feeder is required to feed many substrates into the respective film growing chambers, the substrate feeder is also subject to a feed job conflict in feeding substrates into the film growing chambers.
Such a feed job conflict can be avoided by setting up a suitable feed job schedule for establishing a sequence of individual feed jobs. However, unless a suitable feed job schedule is set up, a substrate may be exposed to an environment in which its temperature cannot properly be controlled for a long period of time, e.g., a substrate may remain gripped by the substrate feeder and stay in an undesirable temperature environment for a long period of time, and may be given an unwanted heating history, resulting in a reduction in substrate yield. This problem also arises with respect to the substrate processing apparatus of the single-substrate in-line processing type, but is more serious with the substrate processing apparatus of the single-substrate cluster type.